Inflatable cuffs have been proposed for applying occlusive pressure to a flow lumen of a patient's body, or for sealing between a medical instrument and a flow lumen of a patient's body. For example, an endotracheal tube may include an inflatable cuff that conforms to the contours of a patient's trachea when inserted into the trachea and inflated to seal a gap between the endotracheal tube and the trachea. Further, syringes have been proposed for inflating an inflatable cuff.
U.S. Pat. No. 4,727,887 (hereinafter “the '887 patent”) describes an artificial sphincter with an occlusion cuff for applying occlusive pressure to a flow lumen of a patient's body (e.g., a urethra). The '887 patent further proposes a combination hypodermic manometer including a piston assembly, which is adapted for reciprocal movement through a fluid-filled sleeve. As the piston assembly of the '887 patent is moved through the sleeve, a bellows is compressed, thereby changing a height of fluid within a manometer fluidly coupled to the bellows.
However, to inflate some occlusion cuffs with less than one full stroke of the hypodermic manometer, the sleeve may require an unduly large internal volume. Further, large sleeve cross sectional areas, which promote the ability to inflate the occlusion cuff with less than one full stroke, impair the ability of the operator to make fine adjustments to the fluid pressure within the occlusion cuff, because small changes in piston position may result in unduly large changes in cuff pressure. Moreover, if the fluid necessary to inflate the occlusion cuff exceeds the volume within the sleeve, then the hypodermic manometer may need to be uncoupled from the occlusion cuff to refill the sleeve before additional fluid can be delivered to the occlusion cuff by subsequent strokes of the piston within the sleeve, thereby impairing the user's ability to make quick and precise changes to the occlusion cuff pressure.
In addition, pressure indicating accuracy of the hypodermic manometer of the '887 patent may depend upon orientation of the manometer with respect to gravity, making it difficult to use with accuracy in practice. Further still, a rupture or leak of the bellows poses the risk of mixing the manometer fluid with the fluid in contact with the occlusive cuff.
Accordingly, methods and apparatus that enable quick and precise adjustments of a pressure within an inflatable cuff, and which enable cuff pressure monitoring that is insensitive to the orientation of the apparatus, are desired.